Cancer's deadly toll grows in less developed countries as new cases increase globally

SEATTLE - While cancer is the world's second leading cause of death after cardiovascular diseases, the chances of getting cancer and dying from it look radically different depending on where you live, according to a new analysis of 32 cancer groups in 195 countries or territories.

The most marked increase in cancer cases between 2005 and 2015 occurred in countries of the lowest development status, where new cases grew by 50%. Authors of the study grouped countries based on their Socio-demographic Index (SDI) - a combined measure of education, income, and fertility. New cancer cases in the highest SDI group - which includes countries like the United States and Japan - grew by 36% over the same period.

"The cancer divide is real and growing," said lead author Christina Fitzmaurice, Assistant Professor at the Institute for Health Metrics and Evaluation (IHME) at the University of Washington. "The number of new cancer cases is climbing almost everywhere in the world, putting an increasing strain on even the most advanced health systems. But the most rapid and troubling escalation can be seen in countries of lower development status, which can ill afford it."

In addition, cancer mortality decreased in many nations over the past decade, but increased in more than 50 countries, most of which are in sub-Saharan Africa. These countries include Kenya, Tanzania, Niger, the Democratic Republic of Congo, Mali, and Senegal, where health services needed to prevent, diagnose, and treat cancer are often missing.

In 2015, there were 17.5 million new cancer cases worldwide and 8.7 million deaths. The disease burden of cancer remains heaviest for countries with the highest levels of development, such as the United States, the United Kingdom, and Germany. Globally, 44% of all new cancer cases and 34% of all cancer deaths are in this highest development group.

New cases of cancer increased globally by 33% between 2005 and 2015. The most common forms of cancer globally are: breast cancer; tracheal, bronchus, and lung (TBL) cancer; and colon and rectum cancer. TBL cancer and colon and rectum cancer top the list of those causing the greatest number of deaths, followed by stomach and liver cancers.

Breast cancer remains both the most common and deadliest form of cancer for women, accounting for 523,000 deaths in 2015. For men, prostate cancer caused the highest number of new cases, but TBL cancer was the number one killer overall, causing 1.2 million deaths globally.

Diverse types of cancer also afflict countries very differently. For example, cervical cancer was ranked the 20th leading cause of death in the United States in 2015; in neighboring Mexico, however, cervical cancer was ranked significantly higher at number eight, with twice the mortality rate. In South Africa, a lower-resource setting, cervical cancer was the second-leading cancer killer, claiming the lives of 5,400 women in 2015.

The authors of the study call on government agencies and the private sector to expand prevention efforts, especially in lower SDI countries where several of the deadliest cancers, such as cervical and liver cancer, are also the most preventable. For example, chronic hepatitis B and C - preventable conditions - are responsible for the majority liver cancer deaths. However, in low SDI countries where childhood immunization to hepatitis B is not universal, the incidence of liver cancer has increased since 2010. Countries where liver cancer tops the list of top cancer killers include Nigeria, Ghana, Egypt, and Thailand.

"Increases in new cancer cases and other noncommunicable conditions will pose heavy strains on health care systems in the coming decades, especially in low-resource communities," said IHME Director Dr. Christopher Murray. "Investments in prevention, screening, and treatment, as well as better measurement to focus efforts, are needed to help reverse these troubling - and preventable - trends."

The report was published today in JAMA Oncology in a study by the Global Burden of Disease collaboration, an international consortium of 2,000 researchers in nearly 130 nations led by IHME.

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